The proposed research will adapt and standardize for clinical use a direct, non-invasive method for measuring human iorn stores by the in vivo determination of hepatic magnetic susceptibility. This safe, rapid and readily applicable technique can now detect iron overload in hemochromatosis, even in the precirrhotic stage, and make possible prevention of tissue damage by prophylactic phlebotomy; previously liver biopsy was required. Changes in iron stores may be monitored in patients being supported with transfusions (Thalassemia; aplastic anemia) or receiving treatment with iron chelators or phlebotomy. It is anticipated that detection of depleted iron stores will be possible with further development of the method. A reliable, non-invasive indicator of hepatic iron stores will provide a means of screening high risk groups for iron deficiency and of assessing the results of programs of iron supplementation, a capability of particular importance in the pediatric age group because of concern that iron lack may adversely affect normal development. By certifying a group of infants and children as iron replete, the method could help establish normal pediatric blood values. Finally, the hepatic magnetic susceptibility is a direct measure of fundamental physical property of storage iron and will be free of the confounding influences which have limited the clinical usefulness of indirect estimates of human iron stores.